Baseball’s Imbalance of Power

One-third of the way into the Major League Baseball season, the two leagues have switched identities. American League teams, which normally have an offensive edge because they can substitute a designated hitter for the pitcher, are being outscored by the National League: AL teams are averaging 4.4 runs per game, to the NL’s 4.59. Five of the eight lowest-scoring teams in the majors are in the AL, and the Kansas City Royals have the second-most-anemic offense, even after scoring eight runs against Minnesota on Wednesday. The average NL team also has hit 4.4 more home runs than the average AL team.

A strikeout by the Royals’ Jose Guillen contributed to their AL-worst offense so far this season. (Associated Press Photo)

Readers Jack Esterly and Matt Viereck brought the offensive imbalance to my attention and wanted to know if the NL has ever outscored the AL since the introduction of the DH in 1973. I checked in with Phil Birnbaum, a fellow sports-numbers aficionado and a winner of my probability quiz last month. In 1974, he found, the NL outscored the AL, 8,070 to 7,976. In every other season featuring the designated hitter, the AL has outscored the NL.

Combining every team in each league (14 in the AL and 16 in the NL) helps smooth over imbalances between teams that the DH can’t overcome — in some seasons the disadvantage of having pitchers swing the bat hasn’t kept every NL team from outscoring the really bad AL teams. If the Royals dip below the San Diego Padres and stay behind everyone else in scoring, they’ll be the 12th AL team in the designated-hitter era to rank last in the majors in scoring, according to Mr. Birnbaum. The most recent AL team to attain this dubious honor was Tampa Bay, back in 2006. (The Rays also trailed all teams in scoring in their 1998 debut, meaning they’ve earned this dishonor twice in 11 seasons of existence.)

Be careful not to interpret these numbers as a shift in the balance of power between the leagues. As AL partisans can tell you, the AL pennant winner has swept three of the last four World Series and the AL All-Stars haven’t lost the Midsummer Classic since 1996. And offense isn’t everything — the lower-scoring league may have vastly superior pitching or fielding. (Baseball Prospectus’s Joe Sheehan suggests teams are intentionally changing their style of play.) Playoff games tend to be lower-scoring affairs. And in the first weekend of interleague play, AL teams won 22 of 41 games — though that’s a small edge over a small sample size.

While the DH isn’t giving the AL an edge so far in offense, Numbers Guy reader James Morgan wondered if, over the history of the rule, the DH has helped AL teams win more World Series. Mr. Birnbaum notes that the AL team has won 20 out of 34, just one standard deviation from the expected total of 17. “Underscoring the non-significance is the fact that consecutive years aren’t completely independent,” he said. “You get teams that are obviously far more talented than others, like the late-’90s Yankees.”

Until 1986, the DH rule alternated being on or off for each World Series. But during that time, the NL won most series with the DH, and the AL won most series without it. In the years in which the DH has been used in the World Series in AL parks but not in NL ones, the home team’s overall record is 71-43. That’s a winning percentage of 62.2%, compared to an expected home winning percentage among evenly matched teams of 54%. (It was 53.7% in other playoff rounds.)

Mr. Birnbaum notes that this effect isn’t statistically significant; it’s a small sample size, with a maximum of seven new data points each year. He didn’t expect to see an effect large enough to attain significance, because the effect of anemic hitting from AL pitchers, or subpar performances from NL DHs, wouldn’t be worth more than a quarter of a run per game — and could be worth far less.

Further reading: San Diego Union-Tribune columnist Chris Jenkins hunts for explanations for the AL power outage, checking in with managers Dusty Baker and Bud Black.

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